SAN DIEGO — Gov. Arnold Schwarzenegger said Friday he will run for re-election next year.

The governor made the announcement, which had been expected, at a rally in San Diego.

The Republican actor-turned-governor, who has hinted as much for weeks, had all but launched a campaign Wednesday, telling supporters, “I’m not in this just for the short term.”

The announcement coincides with the opening day of the state Republican Party convention in Anaheim, which Schwarzenegger is scheduled to address Saturday.

The challengers already are lining up. State Treasurer Phil Angelides and Controller Steve Westly have announced they will seek the Democratic nomination. Two liberal Hollywood luminaries, director Rob Reiner and actor Warren Beatty, also have been mentioned as possible candidates.

Schwarzenegger, whose popularity among Democrats and independents has eroded badly, must generate enthusiasm within his party’s base if several ballot initiatives he has championed are to pass in a Nov. 8 special election.

The initiatives are intended to curb the power of the Democrat-controlled Legislature and allied public employee unions.

Todd Harris, Schwarzenegger's campaign spokesman, said the governor will formally kick off his campaign after the Nov. 8 election.

Strategists had said the governor had to cement his November 2006 re-election plans now to improve his fundraising for the initiatives, which would establish a state spending cap, strip lawmakers of the power to draw political boundaries and make it harder for public school teachers to get tenure. Recent polls show none receiving majority support.

Schwarzenegger was immensely popular his first year, but his job approval ratings have dropped sharply in recent months. His decision to push the ballot measures generated a backlash from labor unions, which have spent millions on television ads since the spring to discredit him.

A nonpartisan Field Poll released last week found that just 36 percent of California voters are inclined to re-elect Schwarzenegger.